[PATCH 6/9] Optimise __aeabi_ldivmod

Richard Earnshaw rearnsha@arm.com
Wed Jun 18 14:03:00 GMT 2014


On 11/06/14 11:19, Charles Baylis wrote:
> 2014-05-22  Charles Baylis  <charles.baylis@linaro.org>
> 
> 	* config/arm/bpabi.S (__aeabi_ldivmod): Perform division using
> 	__udivmoddi4, and fixups for negative operands.

OK.


> ---
>  libgcc/config/arm/bpabi.S | 41 ++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/libgcc/config/arm/bpabi.S b/libgcc/config/arm/bpabi.S
> index 3f9ece5..c044167 100644
> --- a/libgcc/config/arm/bpabi.S
> +++ b/libgcc/config/arm/bpabi.S
> @@ -175,10 +175,49 @@ ARM_FUNC_START aeabi_ldivmod
>  	test_div_by_zero	signed
>  
>  	push_for_divide	__aeabi_ldivmod
> +	cmp	xxh, #0
> +	blt	1f
> +	cmp	yyh, #0
> +	blt	2f
> +	/* arguments in (r0:r1), (r2:r3) and *sp */
> +	bl	SYM(__udivmoddi4) __PLT__
> +	pop_for_divide
> +	RET
> +
> +1: /* xxh:xxl is negative */
> +	negs	xxl, xxl
> +	sbc	xxh, xxh, xxh, lsl #1	/* Thumb-2 has no RSC, so use X - 2X */
> +	cmp	yyh, #0
> +	blt	3f
> +	/* arguments in (r0:r1), (r2:r3) and *sp */
> +	bl	SYM(__udivmoddi4) __PLT__
> +	pop_for_divide
> +	negs	xxl, xxl
> +	sbc	xxh, xxh, xxh, lsl #1	/* Thumb-2 has no RSC, so use X - 2X */
> +	negs	yyl, yyl
> +	sbc	yyh, yyh, yyh, lsl #1	/* Thumb-2 has no RSC, so use X - 2X */
> +	RET
> +
> +2: /* only yyh:yyl is negative */
> +	negs	yyl, yyl
> +	sbc	yyh, yyh, yyh, lsl #1	/* Thumb-2 has no RSC, so use X - 2X */
> +	/* arguments in (r0:r1), (r2:r3) and *sp */
> +	bl	SYM(__udivmoddi4) __PLT__
> +	pop_for_divide
> +	negs	xxl, xxl
> +	sbc	xxh, xxh, xxh, lsl #1	/* Thumb-2 has no RSC, so use X - 2X */
> +	RET
> +
> +3: /* both xxh:xxl and yyh:yyl are negative */
> +	negs	yyl, yyl
> +	sbc	yyh, yyh, yyh, lsl #1	/* Thumb-2 has no RSC, so use X - 2X */
>  	/* arguments in (r0:r1), (r2:r3) and *sp */
> -	bl	SYM(__gnu_ldivmod_helper) __PLT__
> +	bl	SYM(__udivmoddi4) __PLT__
>  	pop_for_divide
> +	negs	yyl, yyl
> +	sbc	yyh, yyh, yyh, lsl #1	/* Thumb-2 has no RSC, so use X - 2X */
>  	RET
> +
>  	cfi_end	LSYM(Lend_aeabi_ldivmod)
>  	
>  #endif /* L_aeabi_ldivmod */
> 




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